For half a century art directors, picture editors, ad execs and publishers have found the Bettmann Archive a source for portraits and unusual illustrations, often historical, on almost any subject, from apple-bobbing to zebra-training. In this appealing memoir (abundantly illustrated with holdings from the Archive), its founder recalls his childhood in Leipzig, Germany's book-trade center, where he was born in 1903. His father, an orthopedic surgeon and an ardent bibliophile, instilled in him a devotion to books, particularly those finely designed and illustrated. The author wrote a doctoral dissertation on literary piracy in the 18th century, supplemented his Ph.D. with a degree in library science and became a curator, all the while developing a carefully indexed picture file. When he fled Nazi Germany in 1935, he painstakingly built up his file into the now-famous picture agency in New York City, a process he recalls with an attractive mix of pride and self-deprecating humor. His experiences with major publishing figures, among them Harry Scherman, Van Wyck Brooks and Harry Abrams, will especially interest those in the trade. (Dec.)